Posted By project_x on 10/25/2008 6:13 PM
For the summer, I am going to install a system to use the furnace discharge water for watering the lawn. Hope this helps, feel free to ask me any questions.

Posted By TechGromit on 10/25/2008 8:18 PM

Interesting Idea. I too have an open loop system, but currently the water just discharges into the woods behind my house. Currently the sprinkler system runs off city water along with the rest of the house. Can you explain how this system is going to work? I would assume when the sprinklers are not on, the discharge would be in bypass mode, but when you want to run the sprinklers, a value would have to close the discharge path and another valve opens to re-direct the water into the sprinkler system. Also I would assume you would have to know how much each water each sprinkler head discharges, so you can have enough heads so no back pressure builds up, which would affect the geothermal system efficency. Also, some system would have to worked out so if the Geothermal system isn't running at the set time for watering the lawn, the lawn would some how still have to get watered, if the timed cycle for watering the lawn passed without the geo system kicking on. 

What steps are you planning on solving these problems?




  

Posted By Alex_in_FL on 10/29/2008 5:52 PM
Sprinkler systems need need 25 - 35 psi water. You are not going to get that from your geothermal circulation pump. Using a much bigger pump will eat into the efficiency of your GSHP. Now if you have a drip irrigation system it might work.

Want to think outside the box? You could discharging the water to your roof during the summer to create a cool roof. This will provide you with a reduced heat load.

Posted By engineer on 10/29/2008 6:52 PM
Supplying a geo heat pump whose waterside heat exchanger needs approx 5 psi with water from a well pump at 50 psi may be "effortless" but costs considerable efficiency.

Posted By tuffluckdriller on 10/30/2008 11:17 AM
What about a cistern underground from the well? Can the well/domestic pump supply a tank to keep it full, and the geo draws from it with its own pump?

Posted By engineer on 10/30/2008 11:22 PM
I'd run them independently, but I can't wrap my mind around how they'd be plumbed...both sown in the same well?

Posted By tuffluckdriller on 10/31/2008 10:31 AM
On possibly low flowing water wells in our area, the smart water well drillers install a tank or two underground for storage. These allow for not over-pumping the well. What these offer,too, is that the home, that's too far from a water system, has both adequate for the domestic use needs, and has a "fire hydrant" value for fire suppression for that house. It lowers people's insurance costs. That's why it came to mind for your project, if you're worried about drawing down the well too much.
[/quote]

It's not that I have a low yield well, it will pump 16gpm all day long from 60 or 70 feet. It's where does the static level go during this time . If the static level always remained at 5ft, a system would be easy, but if the static level goes down while running the furnace, dishwasher, washer and the sprinklers, I need to be able to "lift" enough water to supply at a reasonable flow (16GPM), in order to do this you would need a powerful enough pump. Even with a storage tank, you still need to lift the water to the tank and provide a flow sufficient for the furnace, same issue... I'd have to do the calculations, but even at 15psi, i don't think a 1/16hp pump is going to supply 10gpm to my furnace from 70ft.

Posted By engineer on 10/31/2008 10:51 PM
That dynamic situation definitely changes required pump power and type. Are you sure you aren't overpumping? Open loop can go as low as 1.5 GPM / ton, depending on water temp. Given your pumping situation system efficiency (factoring in pump power) might actually rise if your reduced gpm / ton.